Resize Image

Resizing draws the image onto a canvas of the target dimensions, letting the browser resample the pixels. Scaling down averages groups of source pixels into each output pixel, which is why a reduced image looks clean. The tool asks for high-quality smoothing rather than the fast default, which visibly reduces the jagged edges you get from naive scaling.

Locking the aspect ratio is the default because unlocking it distorts people. With the lock on, typing a width computes the matching height and vice versa. Turn it off only when you genuinely need a fixed frame and know the picture will stretch.

Scaling up is possible and almost always a mistake. A 400px image enlarged to 1600px has no extra detail to draw on — the browser interpolates between the pixels it has, and the result is soft and slightly plasticky. The tool warns when you cross the original size, because it is usually accidental.

Resizing is also the most effective way to shrink a file. Halving both dimensions leaves a quarter of the pixels, which typically means a quarter of the file — a far bigger saving than any quality setting achieves, and with no artefacts.

You are adding a header image to an article. The photo from your camera is coast.jpg: 6000×4000 and 8.4 MB. The article column is 1200px wide.

Choose the file. Both fields fill in with the original dimensions and the ratio lock is on. Tap the Web — 1200px preset: the width becomes 1200 and the height follows to 800 by itself, preserving the 3:2 shape.

Press resize. The result is around 210 KB — a fortieth of the original. Nothing about the picture has been degraded; there are simply twenty-five times fewer pixels, which is all the page ever needed. Serving the 6000px original would have cost every visitor 8.4 MB to display an image at 1200px.

Now the case to avoid. Suppose you only have a 500px thumbnail and want 1200px. Type 1200 and the tool warns you are enlarging. Do it anyway and the result is visibly soft: the browser has invented 1.15 million pixels from 500×333 of real information. No tool can recover detail that was never captured.

If you need a specific shape rather than a specific size — a square avatar from a rectangular photo — cropping is the right tool, because resizing to a square would squash the picture.